static PgpSignatureVerifierLoader getInstance()

in apm-agent-attach-cli/src/main/java/co/elastic/apm/attach/PgpSignatureVerifierLoader.java [59:142]
69 lines of code
10 McCabe index (conditional complexity)

    static PgpSignatureVerifierLoader getInstance(final String sourceLib, final Path targetLib, String verifierClassName) throws Exception {

        // done lazily so that we create the logger only after proper initialization
        final Logger logger = LogManager.getLogger(PgpSignatureVerifierLoader.class);

        Path libPath;
        // first try to see if the lib is available as a resource available to the current class loader
        URL resourceUrl = PgpSignatureVerifierLoader.class.getResource(sourceLib);
        if (resourceUrl != null) {
            URI libUri = resourceUrl.toURI();
            if (libUri.getScheme().equals("jar")) {
                FileSystem fileSystem;
                try {
                    fileSystem = FileSystems.getFileSystem(libUri);
                } catch (FileSystemNotFoundException e) {
                    fileSystem = FileSystems.newFileSystem(libUri, Collections.<String, Object>emptyMap());
                }
                libPath = fileSystem.getPath(sourceLib);
            } else {
                // this allows unit testing
                libPath = Paths.get(libUri);
            }
        } else {
            // try to locate as an external lib
            libPath = Paths.get(sourceLib);
        }

        logger.debug("Traversing [{}] for PGP signature verifier implementation and related dependencies", libPath);

        if (!Files.exists(libPath)) {
            throw new IllegalArgumentException(String.format("%s dir cannot be found", sourceLib));
        }

        final List<URL> urlList = new ArrayList<>();
        Files.walkFileTree(libPath, new FileVisitor<Path>() {
            @Override
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
                return FileVisitResult.CONTINUE;
            }

            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                String fileName = file.getFileName().toString();
                if (fileName.endsWith(".jar")) {
                    boolean copyJar = true;
                    Path jarInTargetLib = Paths.get(targetLib.toString(), fileName);
                    if (Files.exists(jarInTargetLib)) {
                        logger.trace("{} already exists at {}", fileName, targetLib);
                        if (Files.isReadable(jarInTargetLib)) {
                            copyJar = false;
                        } else {
                            // quick and dirty - this is a temporary solution until we download agent from the Fleet package registry
                            logger.info("{} is not readable for the current user, removing and copying new one", jarInTargetLib);
                            Files.delete(jarInTargetLib);
                        }
                    }
                    if (copyJar) {
                        logger.debug("Copying {} to {}", fileName, targetLib);
                        Files.copy(file, jarInTargetLib);
                    }
                    urlList.add(jarInTargetLib.toUri().toURL());
                }
                return FileVisitResult.CONTINUE;
            }

            @Override
            public FileVisitResult visitFileFailed(Path file, IOException exc) throws IOException {
                throw exc;
            }

            @Override
            public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
                return FileVisitResult.CONTINUE;
            }
        });

        if (urlList.isEmpty()) {
            throw new IllegalArgumentException(String.format("%s dir is empty", sourceLib));
        } else {
            logger.debug("{} directory contents: {}", sourceLib, urlList);
        }

        return new PgpSignatureVerifierLoader(urlList.toArray(new URL[0]), verifierClassName);
    }